Variable inertia flywheel

ABSTRACT

Variable inertia flywheels are used in power generation apparatus to quickly release stored kinetic energy to meet transient power load demands. Such flywheels typically vary inertia by using either interconnected multiple flywheels having different inertia or by mechanically moving a mass connected with the flywheel radially with respect to the axis of rotation. A variable inertia flywheel according to the present invention comprises a body and a number of fluid movement devices disposed at equal angular intervals about the rotational axis of the body. Each device comprises at least first and second chambers axially aligned in a substantially radial direction and adapted to contain an electrolytic fluid. The first and second chambers are interconnected by a channel that permits transfer of the fluid between the chambers. The movement of the fluid between the chambers is facilitated by an electromagnetic pump.

TECHNICAL FIELD

The present invention relates to a rotating, kinetic energy storagedevice, and in particular to a variable inertia flywheel utilizingelectromagnetic pumps.

BACKGROUND

Variable inertia flywheels are utilized in rotating machinery to storeenergy that may be quickly released should there be a sudden energydemand. Such flywheels are common in the field of electrical powergeneration. Known variable inertia flywheels vary inertia either byinterconnecting multiple flywheels having different inertia or by movinga mass connected with the flywheel radially with respect to the axis ofrotation. The moveable mass can be a solid block or it can also be aliquid. One example, where the movement of liquid is facilitated by wayof electromechanical pumps can be seen in U.S. Pat. No. 4,735,382.

However, the more moving parts any apparatus has, the greater the chanceof failure during its working life. Additionally, known mechanical andelectro-mechanical arrangements lack responsiveness when dealing with asudden increase in demand for power.

The present invention is directed to overcoming one or more of theproblems identified above.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a variable inertiaflywheel comprising a body and a plurality of fluid movement devicesdisposed at angular intervals about the axis of rotation of the body.Each of the devices comprises at least first and second chambers adaptedto contain an electrolytic fluid, the chambers being radially spacedfrom each other; and at least one electromagnetic pump for the movementof the fluid between the first and second chambers.

According to another aspect of the present invention, a method ofvarying the inertia of a flywheel comprising applying an electric fieldto an electrolytic fluid to move said fluid from a first chamberprovided in said flywheel to a second chamber provided in said flywheel,the second chamber being radially spaced from the first chamber.

In accordance with another aspect of the present invention, a method ofgenerating electrical power in a power generation apparatus comprisesdetermining a load demand with a control system, transmitting a demandsignal from the control system to a variable inertia flywheel, varyingthe inertia of the flywheel in response to the demand signal by movingfluid from a first chamber provided in the flywheel to a second chamberprovided in the flywheel, the first chamber being radially spaced fromthe second chamber, and transferring the stored kinetic energy from theflywheel to the generator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a variable inertia flywheel;

FIG. 2 shows a view of a portion of the variable inertia flywheel shownin FIG. 1; and

FIG. 3 shows a schematic diagram of an electrical power generationapparatus incorporating the present invention.

DETAILED DESCRIPTION

The preferred embodiment described herein shows a rotating, kineticenergy storage device. The energy storage device, or flywheel, may beused with a power generation apparatus. The flywheel useselectromagnetic pumps to move electrolytic fluid between fluid chambersin order to vary the moment of inertia of the flywheel.

With reference to FIG. 1, there is shown a schematic view of theinternal layout of a variable inertia flywheel 10. The flywheel 10 isformed from a solid disc body 12 in which are located one or more setsof chambers 14,16,18. In the embodiment described herein, the flywheel10 is provided with a pair of fluid movement devices that are locateddiametrically opposite one another on the flywheel 10. Each devicecomprises inner 14, intermediate 16 and outer 18 chambers. The threechambers 14,16,18 are spaced from one another in a radial directionrelative to the axis of rotation 20 of the flywheel 10. Each devicefurther comprises capillary tubes, or channels, 22 of fused silica whichconnect the inner and intermediate chambers 14,16 and the intermediateand outer chambers 16,18. The capillary tubes 22 connect the chambers14,16,18 at openings 14 a, 16 a, 18 a on the radially outermost end ofeach chamber, that is, the ends of the chambers distal the rotationalaxis 20 of the flywheel 10. In the case of the intermediate chamber 16,there are two openings 16 a located at either corner of the chamber 16such that the intermediate chamber 16 communicates with both the innerand outer chambers 14,18.

As best seen in FIG. 2, each device is provided with an electromagneticpump 24, which is a pump for conducting fluid without the use of movingparts. Electromagnetic pumps suitable for this purpose have beendeveloped by Sandia Corporation of California, USA and are described indetail in U.S. Pat. Nos. 6,013,164, 6,019,882, 6,224,728, and 6,277,257.

The pumps 24 have no moving parts as each uses the principles ofelectro-osmotic flow to move the fluid. Each pump 24 comprises anelectrically energizable coil 26 wrapped around the capillary 22 andconnected to a power supply 30. The power supply 30 includes acommercially available slip ring arrangement to power all the pumps. Apair of spaced-apart electrodes 28 is located inside the capillary andis also connected to the power supply 30. The fluid 32 contained in thechambers 14,16,18 and capillaries 22 is an electrolyte solution (i.e. asolution containing ions and capable of ionic conduction). In theembodiment described here, the fluid 32 is a solution of water andtrisodium phosphate.

Industrial Applicability

The present invention varies the inertia of the flywheel 10 by movingthe electrolytic fluid 32 between the chambers 14,16,18. The manner inwhich the fluid 32 is moved between the chambers 14,16,18 can bedescribed best with reference to FIG. 2.

The specific embodiment described herein relates to a flywheel for usewith a power generation apparatus, as shown in FIG. 3. The apparatuscomprises a control system 40, a generator driving device such aninternal combustion engine 42, a variable inertia flywheel 10 and apower generator 44. The control system 40 has control over both theengine 42 and flywheel 10 via a pair of control inputs 48 a, 48 b. Thecontrol system 40 receives input signals 46 that indicate the presentpower demand and whether a steady state or transient load is requiredfrom the generator 44. If the generation apparatus receives an inputsignal 46 requiring a change from a steady state load to a transientload, it will be necessary to quickly reduce the moment of inertia ofthe flywheel 10, and hence the stored kinetic energy therein, in orderto meet the extra demand. Thus, the control system 40 sends a signal viacontrol input 48 b to the flywheel 10 to reduce the moment of inertiathereof. As the moment of inertia is reduced, the kinetic energy of theflywheel 10 is transferred 50 to the generator 44, allowing thegenerator to increase the amount of power generated through an outlet52.

Referring again to FIG. 2, to reduce the moment of inertia, theelectrolytic fluid 32 in the flywheel must be pumped towards the axis ofrotation 20 of the flywheel 10. In the embodiment described herein,there are two sets of three chambers 14,16,18 positioned diametricallyopposite one another on the flywheel 10. To reduce the moment of inertiaof the flywheel 10 to a minimum it is necessary to pump the fluid 32into the inner chambers 14 from the intermediate 16 or outer chambers18.

The method of operation of the pumps 24 between the chambers 14,16,18 isthe same, whether fluid 32 is being pumped from the outer 18 orintermediate 16 chambers. As the openings 14 a,16 a,18 a of the chambers14,16,18 are located on the outermost edges of the chambers 14,16,18,the centrifugal force of the rotating flywheel 10 ensures that the fluid32 will always be in the ideal position within the chamber 14,16,18 forpumping. Once the energy demand has been received by a control system(not shown), the control system will then send a signal to the pumps 24of the respective sets of chambers to pump the fluid 32 to the innerchamber 14.

Upon receipt of the signal from the control system, the pumps 24 applyan electric potential between the electrodes 28 and an electromagneticfield in the coil 26 by way of the power supply 30. The electrodes 28are in contact with the electolyte 32 contained within the capillaries22. The direction of flow of the electrolyte 32 is determined by thepolarity of the applied electric potential. Furthermore, the flow rateof the electrolyte 32 is determined by the magnitude of the appliedelectric potential, where the flow rate will increase in proportion toan increase in electric potential. Thus, to move the electrolytic fluid32 in the opposite direction (i.e. to pump from the inner chamber 14towards the intermediate 16 and outer chambers 18), the polarity of theelectric potential applied between the electrodes and through the coilis simply reversed.

The present invention enables the inertia of a flywheel to be adjustedby moving a fluid between chambers using hydraulic pumps that, due tothe application of electro-osmotic flow properties, require no movingparts. As there are no moving parts in the pumps, the pumps will not besusceptible to frictional wear unlike conventional mechanical fluidmovement systems. Furthermore, as the system of fluid movement withinthe flywheel is electrical rather than mechanical, it can be rapidlyturned on and off to provide a more instantaneous response to suddenenergy demands compared with conventional flywheel arrangements. Asapparent, the inertia of the flywheel can be varied to transmit storedenergy to the generator while maintaining the power output of theinternal combustion engine at a constant level.

Although the above description is of one particular embodiment of thepresent invention, modifications and improvements can be incorporatedwithout departing from the scope of the invention. For example, byvarying the number of fluid movement devices on the flywheel and/or thenumber of chambers in each fluid movement device, the inertia of theflywheel can be controlled more accurately than existing variableinertia flywheels. Hence, each device could be provided with two, threeor more chambers depending on the operational requirements of theflywheel. The flywheel can also be provided with two or more fluidmovement devices, so long as each device is disposed symmetrically aboutthe axis of rotation of the flywheel to maintain balance. Furthermore,the capillaries may take a number of forms in addition to the silicastructure given as an example herein, while the electrolytic fluid maybe any solution containing ions and being capable of ionic conduction.Although the preferred embodiment of the flywheel has only one slip ringarrangement for powering the pumps, an alternative arrangement may alsobe used. In the alternative arrangement, a slip ring arrangement isprovided for each level of pumps, that is one arrangement for poweringthe pumps between the outer and intermediate chambers and onearrangement for powering the pumps between the intermediate and innerchambers. Those skilled in the art will also recognize that certainaspects of this invention may be implemented with suitable pumps otherthan the electromagnetic pumps described above.

1. A variable inertia flywheel comprising a body and a plurality offluid movement devices disposed about the axis of rotation of the body,each of the devices comprising: at least first and second chambersadapted to contain an electrolytic fluid, the chambers being radiallyspaced from each other; and at least one electromagnetic pump for themovement of the fluid between the first and second chambers.
 2. Thevariable inertia flywheel of claim 1, wherein the first and secondchambers are formed within the body.
 3. The variable inertia flywheel ofclaim 1, wherein the first and second chambers are axially aligned in asubstantially radial direction relative to the axis of rotation.
 4. Thevariable inertia flywheel of claim 1, wherein each fluid movement devicefurther comprises at least a first channel permitting transfer of thefluid between the first and second chambers.
 5. The variable inertiaflywheel of claim 1, wherein the electromagnetic pump comprises: anelectrically energizable coil disposed about the exterior of the firstchannel; a pair of electrodes spaced from one another and incommunication with the electrolytic fluid; and a power supply forapplying an electric potential to the electrodes and the coil.
 6. Thevariable inertia flywheel of claim 1, wherein each chamber has an outerend disposed distal the rotational axis and where its respective channelopens into the chamber adjacent the outer end, the chamber being adaptedsuch that the fluid is urged toward the outer end under the action ofcentrifugal force.
 7. The variable inertia flywheel of claim 1, whereineach of the devices comprises first, second and third chambers, andfirst and second electromagnetic pumps for the movement of fluid betweenthe first and second and second and third chambers, respectively.
 8. Thevariable inertia flywheel of claim 1, wherein the plurality of fluidmovement devices are disposed at equal angular intervals about the axisof rotation of the body.
 9. The variable inertia flywheel of claim 1,wherein the electrolytic fluid is a solution of water and trisodiumphosphate.
 10. A power generation apparatus, comprising: a generatordriving device; a variable inertia flywheel according to claim 1drivingly connected with the generator driving device; and a generatordrivingly connected with the variable inertia flywheel.
 11. The powergeneration apparatus of claim 10, further comprising: a control systemadapted to determine a load demand and operable to control the inertiaof said variable inertia flywheel in response to the determined loaddemand.
 12. The power generation apparatus of claim 10, wherein thegenerator driving device includes an internal combustion engine.
 13. Amethod of varying the inertia of a flywheel comprising applying anelectric field to an electrolytic fluid to move said fluid from a firstchamber provided in said flywheel to a second chamber provided in saidflywheel, the first chamber being radially spaced from said secondchamber.
 14. A method of generating electrical power in a powergeneration apparatus comprising a control system, a generator drivingdevice, a variable inertia flywheel, and a generator, the methodcomprising the steps of: determining a load demand with the controlsystem; transmitting a demand signal from the control system to thevariable inertia flywheel; varying the inertia of the flywheel inresponse to the demand signal by moving fluid from a first chamberprovided in said flywheel to a second chamber provided in said flywheel,the first chamber being radially spaced from said second chamber, andtransferring stored kinetic energy from the flywheel to the generator.15. The method of claim 14, wherein said stored kinetic energy istransferred from the flywheel to the generator as a result of change inthe inertia of the flywheel.
 16. The method of claim 15 wherein saidflywheel comprises the flywheel of claim 1, wherein the fluid comprisesan electrolytic fluid, and wherein said varying step includes applyingan electric field to the electrolytic fluid to move said fluid from thefirst chamber to the second chamber.
 17. The method of claim 15, furthercomprising: during the varying and transferring step, maintaining apower output of the generator driving device at a substantially constantlevel.
 18. The method of claim 14 wherein said load demand includes atransient load demand for electrical power from the electrical powergeneration apparatus.
 19. A method of generating electrical power in apower generation apparatus comprising a control system, a generatordriving device, a variable inertia flywheel, and a generator, the methodcomprising the steps of: determining a load demand with the controlsystem; transmitting a demand signal from the control system to thevariable inertia flywheel; varying the inertia of the flywheel inresponse to the demand signal by moving fluid from a first chamberprovided in said flywheel to a second chamber provided in said flywheel,the first chamber being radially spaced from said second chamber; andtransferring stored kinetic energy from the flywheel to the generator;wherein said flywheel comprises the flywheel of claim 1, wherein thefluid comprises an electrolytic fluid, and wherein said varying stepincludes applying an electric field to the electrolytic fluid to movesaid fluid from the first chamber to the second chamber.
 20. A method ofgenerating electrical power in a power generation apparatus comprising acontrol system, a generator driving device, a variable inertia flywheel,and a generator, the method comprising the steps of: determining a loaddemand with the control system; transmitting a demand signal from thecontrol system to the variable inertia flywheel; varying the inertia ofthe flywheel in response to the demand signal by moving fluid from afirst chamber provided in said flywheel to a second chamber provided insaid flywheel, the first chamber being radially spaced from said secondchamber; transferring stored kinetic energy from the flywheel to thegenerator; and during the varying and transferring steps, maintaining apower output of the generator driving device at a substantially constantlevel.